This invention relates generally to the synthesis of carbon, particularly in an activated form, from sludge and, in particular, from waste sludge such as composed of biosolids and the like.
In view of factors such as increased relative quantities of sludge materials such as produced or formed at wastewater treatment, paper mill processing and the like facilities and limited disposal areas for such sludge materials, there is an increasing need and demand for processing techniques whereby such sludge materials can be transformed or converted into other, possibly more desirable and useful, materials.
Biosolids is the waste sludge such as produced at wastewater treatment facilities and as may result from various bioreactions. Biosolids, also sometimes called or referred to as the sludge or residue of sewage treatment processes, are typically nutrient-rich by-products of specially treated or stabilized wastewaters originating from municipalities, industries or storm water runoff, for example, and typically produced in relatively high mass rates.
Activated carbon is a frequently used adsorbent material and has virtually displaced many other materials in use as adsorbents in various solvent recovery systems. Activated carbon is a generally superior adsorbent at least in part because of desirable surface properties. The unique adsorption capability of activated carbons is generally related to such carbon materials having a high adsorption capacity and a high degree of surface porosity and such as may relate to carbon materials desirably having relatively high surface areas and significant microporous structure. In general, pores are classified by size in one of three categories or classes: micropores (pores having a width less than 2 nm), mesopores (pores having a width of 2 nm and 50 nm), and macropores (pores having a width in excess of 50 nm).
Activated carbons are used extensively for or in various industrial applications including: solvent recovery, gas refining, air purification, exhaust desulfurization, deodorization and gas separation and recovery, for example. The application of activated carbons in water treatment includes: removal of color, odor, taste or other undesirable impurities from water; treatment of domestic and industrial wastewaters; and collection and recovery of solutes such as gold and silver, for example. In addition, activated carbons have found application as catalysts in various chemical processes.
In practice, the activity as well as possibly the effectiveness of such carbon material in particular adsorbent or catalyst applications may be limited by either or both the surface area and porosity of the activated carbon material. The production or formation of such activated carbon material from selected chemical processing waste streams has been generally limited or restricted due to limitations in either or both the surface area and porosity of the resulting activated carbon material.
Thus, there is a need and a demand for economical and environmentally sound solutions to biosolids management and reuse at treatment facilities at various locations in the world. In particular, there is a need and a demand for techniques whereby such raw material or wastewater streams can be processed or otherwise treated such as to produce or form activated carbon of either or both increased surface area and increased microporosity. Further, there is a need and a demand for activated carbon having either or both increased surface area and increased microporosity and such as formed from such process streams.